PD-1 Haplotype Combinations and Susceptibility of Patients to Squamous Cell Carcinomas of Head and Neck

Introduction: Head and neck squamous cell carcinomas (HNSCCs) are the most common cancers of head and neck and the sixth most common malignancy worldwide. Programmed cell death 1 (PD-1) is an immune inhibitory molecule which through interaction with its ligands recruits protein phosphatase resulting in immune response inhibition. Expression of PD-1 ligands on tumor cells is considered as one of the crucial immune evasion mechanisms. This study aimed to investigate the association of PD-1 gene polymorphisms at positions PD1.3 (rs11568821), PD1.5 (rs2227981) and PD1.9 (rs2227982) with susceptibility to HNSCCs.

Subjects and methods: 150 patients pathologically confirmed to suffer from HNSCCs and 150 age-sex matched healthy controls were recruited in this study. Genomic DNA was extracted from white blood cells of all participants. Restricted fragment length polymorphisms (RFLP)-PCR was performed using site specific primers to determine the genotypes in each position.

Results: Statistical analyses indicated no significant differences in the frequencies of genotypes, alleles as well as haplotypes between patients and controls (P > 0.05), however, haplotype combination differed significantly between two groups. GCC/GCT, GCC/GCC and GCT/GCC were higher in the HNSCC patients than the control group (P < 0.05). On the other hand, in the controls, GCT/GCT, GCT/ACC, GCT/ACT and ACC/GCT were more frequent. No significant association was found with various HNSCC clinicopathological characteristics.

Discussion: Our results suggested that although PD-1 gene polymorphisms at three investigated positions are not solely associated with susceptibility to HNSCCs, haplotype combinations emerged from these three loci may render susceptibility.